Study finds obesity can spread through communities like a "social contagion"

A fascinating new study is suggesting that if you move to a community or town with a high rate of obesity, it could increase your own risk of becoming obese. Accounting for other factors that could result in obesity, such as genetics and shared environment, the researchers conclude that to some degree obesity could be considered a "social contagion."

"Social contagion in obesity means that if more people around you are obese, then that may increase your own chances of becoming obese," explains one of the authors of the study, Ashlesha Datar. "In other words, living in a community where obesity is more common can make sedentary lifestyles, unhealthy eating and overweight or obesity more socially acceptable."

The study cleverly focused on military families as they are often assigned to locations they have no choice over, which eliminates the self-selection bias determining where someone would choose to live. Some 1,314 parents and 1,111 children were recruited to take part in the study, which spanned 38 different locations across the United States.

The obesity rates in the counties studied ranged from the low end in El Paso County, Colorado with around 21 percent of adults obese, to the high end in places such as Vernon County, Louisiana with 38 percent of adults obese. The study did indeed find that families assigned to counties with high obesity rates were more likely to be overweight or obese, and vice versa.

"If a family moves to a county with a low obesity rate, such as El Paso County in Colorado where about 21 percent of adults are obese, the parent's chances of being obese would decrease by 29 percent," adds Datar. "The child's chances of being overweight or obese also would decrease by 23 percent."

One of the key aspects of the research was accounting for a distinction between environmental factors that could explain the increased obesity rates, and the idea of obesity as a social contagion. Obviously, if a community doesn't have many gyms or does have a large volume of fast food restaurants they would be environmental factors that could explain the higher obesity rates, so the researchers accounted for many of these built environment factors as covariates in the model, but the obesity connections were still were apparent, suggesting other factors were at play.

"We cannot say for sure that we accounted for everything that might influence eating and exercise behaviors," says Datar. "But we did account for things that researchers in this field typically measure and found that shared environments did not play a critical role in explaining our results."

This isn't the first research to suggest that obesity can spread throughout a community in a way similar to that of a contagious virus. A study published in the New England Journal of Medicine in 2007 examined an interconnected social network of 12 thousand people, and whether weight gain in one person could be connected to weight gain in their friends or family.

The study followed individuals over 30 years and identified each person's weight fluctuations over that time. This resulted in some incredibly thought-provoking conclusions. The researchers found that a person was 57 percent more likely to become obese if a friend became obese, and if the friendship was very close, that risk factor tripled. Interestingly, this effect was not seen in relation to neighbors, but siblings becoming obese did increase the chances of other siblings becoming obese at a level slightly lower than the influence of fiends.

The results from these studies certainly suggest that the so-called obesity epidemic could perhaps be more literally true than previously thought. Sure, obesity isn't a tangible virus that spreads from person to person, but it does seem to pervasively spread via social influence throughout a community or social network.

It's important to note that the takeaway here isn't to blame or ostracize obese people, but rather we should all be aware of the unconscious social cues that could be affecting our well being. Both studies suggest that while obesity begets obesity, the opposite is also true, so a healthy, thin person can effectively influence their friends and community in a positive way.